In rotary electric motors for a vehicle, a full-wave rectification system using diodes as rectifying elements is generally known. For higher efficiency, a rectification system using switching elements as the rectifying elements so as to reduce a loss generated due to the rectifying elements is increasingly used.
There has already been proposed a power converter for a vehicle, which is configured to use the switching elements as the rectifying elements and obtain an estimated angular position at which the diodes are turned ON and OFF through a phase-locked loop circuit so as to control ON and OFF of the switching elements based on the estimated angular position without mounting a rotational position detecting sensor (see, for example, Patent Literature 1).